The present invention relates to a device for detecting a leak in the membrane sealing of a metering cylinder, for use in machines having the metering cylinder and adapted to fill containers with a specified quantity of liquid such as fluid food.
Filling machines of this type are known which comprise a metering cylinder for charging a filling nozzle with a specified quantity of liquid at a time, a piston accommodated in the metering cylinder and having a skirt opposed to the peripheral wall of the cylinder with a clearance formed therebetween, and a membrane closing each open end of the clearance to form a closed space in the clearance.
The membrane has a limit of durability and is periodically replaced when exceeding the limit. However, some membranes develop a leak, such as a pinhole, before the lapse of the period. Thus, there arises a need to discontinue the operation of the machine upon detecting such a leak. The following device is used for detecting leaks.
The metering cylinder has connected thereto a vacuum pipe in communication with the closed space between the cylinder and the piston. The vacuum pipe is provided at an intermediate portion thereof with a tank equipped with a pressure gauge and an electrode rod. When air leaks, the pressure gauge as observed with the eye indicates a variation in the internal pressure of the tank, notifying the operator of the leak. If the leakage fluid is liquid, the electrode rod detects the liquid collected in the tank, indicating the leak.
When leaks are as small as pinholes, the pressure gauge fails to detect the leak accurately since the resulting variation in pressure is small. This drawback is attributable further to the fact that the piping system including the vacuum pipe inevitably permits leakage in its entirety. The electrode rod requires a considerable period of time for an amount of liquid to collect in the tank.